Cancer is a disease resulting from an abnormal growth of tissue. Certain cancers have the potential to invade into local tissues and also metastasize to distant organs. This disease can develop in a wide variety of different organs, tissues, and cell types. Therefore, the term “cancer” refers to a collection of over a thousand different diseases.
Over 4.4 million people worldwide were diagnosed with breast, colon, ovarian, lung, or prostate cancer in 2002 and over 2.5 million people died of these devastating diseases (Globocan 2002 Report). In the United States alone, over 1.25 million new cases and over 500,000 deaths from cancer were predicted in 2005. The majority of these new cases were expected to be cancers of the colon (˜100,000), lung (˜170,000), breast (˜210,000) and prostate (˜230,000). Both the incidence and prevalence of cancer is predicted to increase by approximately 15% over the next ten years, reflecting an average growth rate of 1.4% [1].
Accumulating evidence suggests that cancer can be envisioned as a “signaling disease”, in which alterations in the cellular genome affecting the expression and/or function of oncogenes and tumor suppressor genes would ultimately affect the transmission of signals that normally regulate cell growth, differentiation, and programmed cell death (apoptosis). Unraveling the signaling pathways that are dysregulated in human cancers has resulted in the design of an increasing number of mechanism-based therapeutic agents [2]. Signal transduction inhibition as a therapeutic strategy for human malignancies has recently met with remarkable success, as exemplified by the development of Gleevec for the treatment of chronic myelogenous leukemia (CML) and gastrointestinal stromal tumors (GIST), heralding a new era of “molecularly-targeted” therapies [3-5].
The mitogen-activated protein kinase (MAPK) module is a key integration point along the signal transduction cascade that links diverse extracellular stimuli to proliferation, differentiation and survival. Scientific studies over the last twenty years have led to a quite detailed molecular dissection of this pathway, which has now grown to include five different MAPK subfamilies [extracellular signal-regulated kinases ERK-1/2, c-Jun-N-terminal kinases (JNKs), p38 kinases, ERK-3/4, and ERK-5], with distinct molecular and functional features [6-8]. While certain subfamilies, such as the p38 family, are becoming therapeutic targets in inflammatory and degenerative diseases, the MAPK cascade that proceeds from Ras to ERK-1/2 (the main mitogenic pathway initiated by peptide growth factors) is starting to emerge as a prime target for the molecular therapy of different types of human cancers [9-11], The MAPK pathway is aberrantly activated in many human tumors as a result of genetic and epigenetic changes, resulting in increased proliferation and resistance to apoptotic stimuli. In particular, mutated oncogenic forms of Ras are found in 50% of colon and >90% of pancreatic cancers [12]. Recently, BRAF mutations have been found in >60% of malignant melanoma [13]. These mutations result in a constitutively activated MAPK pathway.
The modular nature of the Raf/MEK/ERK cascade becomes less pleiotropic at the crossover point that is regulated by MEK [14]. No substrates for MEK have been identified other than ERK-1/2. Phosphorylated ERK is the product of MEK activity and thus its detection in cancer cells and in tumor tissues provides a direct measure of MEK inhibition. The selectivity of MEK for ERK1/2 coupled with the availability of antibodies specific for the dually phosphorylated and activated form of ERK, makes MEK an attractive target for anticancer drug development.
First-generation MEK inhibitors, PD98059 [15] and U0126 [16], do not appear to compete with ATP and thus are likely to have distinct binding sites on MEK; these compounds have been extensively used in model systems in vitro and in vivo to attribute biological activities to ERK1/2. A second-generation MEK1/2 inhibitor, PD184352 (now called CI-1040), has an IC50 in the low nanomolar range, enhanced bioavailability, and also appears to work via an allosteric, non ATP-competitive mechanism [17]. Oral treatment with CI-1040 has been shown to inhibit colon cancer growth in vivo in mouse models [18] and this compound was evaluated in phase I/II clinical trials in humans where it eventually failed because of insufficient efficacy [19]. Allosteric MEK inhibitors have recently entered the clinic but were found to have limitations such as poor exposure profiles and/or toxicity issues. Small molecules MEK inhibitors have been disclosed, including in US Patent Publications Nos. 2003/0232869, 2004/0116710, 2003/0216420 and in U.S. patent application Ser. Nos. 10/654,580 and 10/929,295 each of which is hereby incorporated by reference. A number of additional patent applications have appeared in the last few years including U.S. Pat. No. 5,525,6625; WO 98/43960; WO 99/01421; WO 99/01426; WO 00/41505; WO 00/41994; WO 00/42002; WO 00/42003; WO 00/42022; WO 00/42029; WO 00/68201; WO 01/68619; WO 02/06213; WO 03/077914; WO 03/077855; WO 04/083167; WO 05/0281126; WO 05/051301; WO 05/121142; WO 06/114466; WO 98/37881; WO 00/35435; WO 00/35436; WO 00/40235; WO 00/40237; WO 01/05390; WO 01/05391; WO 01/05392; WO 01/05393; WO 03/062189; WO 03/062191; WO 04/056789; WO 05/000818; WO 05/007616; WO 05/009975; WO 05/051300; WO 05/051302; WO 05/028426; WO 06/056427; WO 03/035626; and WO 06/029862.
Despite advancements in the art, there remains a need for cancer treatments and anti-cancer compounds. More specifically, there remains a need for structurally novel MEK inhibitors with a balanced potency-properties profile. It would be especially desirable to identify novel MEK inhibitors which incorporate structural motifs which have not been previously exemplified as being compatible with potent MEK inhibition. It would be especially favorable if these structural motifs would further allow for improvement of MEK potency and/or modulation of compound properties (including physico-chemical, pharmacodynamical and pharmacokinetical properties).
None of the prior art described or cited supra describe the substituted amido phenoxybenzamide compounds of general formula (I) of the present invention, as described and defined herein, and as hereinafter referred to as “compounds of the present invention”, or their pharmacological activity. It has now surprisingly been found, and this constitutes the basis of the present invention, that said compounds of the present invention, which possess a substituted amido phenoxybenzamide moiety, have unexpected and advantageous properties, in particular, said compounds are potent and selective MEK inhibitors. Said compounds of the present invention inhibit activation of the MEK-ERK pathway and show anti-proliferative activity against cancer cells. Compounds and compositions described herein, including salts, metabolites, solvates, solvates of salts, hydrates, prodrugs such as esters, polymorphs, and stereoisomeric forms thereof, exhibit anti-proliferative activity and are thus useful to prevent or treat the diseases or disorders associated with hyper-proliferation as described herein.